1. Field of the Invention
The present invention relates to a donor substrate for laser induced thermal imaging (LITI) and a method of fabricating an organic light emitting diode (OLED) using the same, and more particularly, to a donor substrate for laser induced thermal imaging (LITI) and a method of fabricating an OLED using the same. The OLED and the method of fabricating the OLED of the present invention prevent a transferred emission layer from being damaged by heat and thus prevent wrinkles from forming on the surface thereof.
2. Description of Related Art
Among flat panel displays (FPDs), an organic light emitting diode (OLED) display has the advantages of self-emissive, wide viewing angle, rapid response time, small thickness, low manufacturing cost, high contrast, and the like. For these reasons, the OLED display has attracted much attention as the next-generation flat panel display device.
In general, the OLED includes several layers such as a hole injection layer, a hole transport layer, an organic emission layer, an electron transport layer, an electron injection layer, and the like, which are interposed between an anode and a cathode. A full color display can be realized by patterning emission layers for representing three primary colors of red (R), green (G) and blue (B) on the OLED.
A multi-layered organic layer may be formed by vacuum deposition using a shadow mask or by conventional photolithography. However, in the case of vacuum deposition, there is a difficulty in forming the organic layer into a highly precise pattern, and thus manufacture of a perfect full color display is difficult. Moreover, in the case of photolithography, there is a problem in that the organic layer may be damaged by a developing solution or an etching solution, which results in deterioration of luminous efficiency and lifetime.
Accordingly, a method of patterning the organic layer by laser induced thermal imaging (LITI) has been introduced to solve such problems.
LITI is a method of forming a pattern by transferring a material for forming the pattern onto an acceptor substrate using a laser beam emitted from a laser source. To perform such a method, a donor substrate onto which a transfer layer is formed, a laser source, and an acceptor substrate are required.
The donor substrate includes a base layer, a light-to-heat conversion layer, and a transfer layer including an emission layer. In a transfer process using the donor substrate, when a laser beam is applied onto a predetermined region of the base layer, energy of the laser beam is converted into heat in the light-to-heat conversion layer, and the heat changes the adhesion between the transfer layer and the light-to-heat conversion layer so that a predetermined region of the transfer layer is transferred onto the acceptor substrate.
In the contemporary method of forming the emission layer of the OLED using the donor substrate for LITI, the transfer layer including the emission layer is formed on the light-to-heat conversion layer, and the transfer layer is transferred onto the acceptor substrate by applying the laser beam. In this case, there is a problem in that the emission layer included in the transfer layer is damaged by heat and thus wrinkles are formed on the surface of the transferred emission layer, and interface characteristics deteriorate. Moreover, there is a problem in that, since transfer characteristics vary according to the kind of material used to form the emission layer, the thickness or properties of the emission layer may be changed after transfer, even if the same laser beam is applied.